Mastering Rust - Second Edition

Directory as module

We can also create a directory that represents a module. This approach allows us to have submodules within modules as a file and directory hierarchy. Let's assume that we have a directory, my_program, that has a module named foo as a file foo.rs. It contains a type called Bar along with foo's functionality. Over time, the Bar APIs have grown in number and we wish to separate them as a submodule. We can model this use case with directory-based modules.

To demonstrate creating modules as directories, we have created a program in a directory named my_program. It has an entry point in main.rs and a directory named foo. This directory now contains a submodule within it named bar.rs.

Following is the structure of the directory ...